I. Field of the Invention
This invention relates generally to a forced air heating system, and more specifically to the construction and operation of a solid fuel burning furnace which is designed to operate in conjunction with a conventional fluid (gas or oil) fueled furnace so that compatibility exists.
II. Discussion of the Prior Art
With the availability of fuel oil and natural gas in limited supply, it becomes advantageous to utilize solid fuel including wood and coal as an auxiliary heat source in homes and commercial establishments. Thus, it is desirable to have a solid fuel burning unit which can be tied in directly with a conventional natural gas or oil burning furnace in a forced air heating system.
There is disclosed in the prior art furnace structures which are specially designed to utilize both solid and fluid fuel. For example, the structure set forth in the Gifford U.S. Pat. No. 776,053 allows solid fuel to be burned in a firepot and a fluid-fuel burner is included in the same furnace cabinet but separated from the solid fuel burning portion by suitable baffle plates. Thus, it is not new in the art to utilize both solid fuel and fluid fuel in a same furnace structure. Similarly, the Biddle et al U.S. Pat. No. 2,713,861 describes a stove used for cooking purposes which may be alternately fueled with either a solid fuel or a fluid fuel.
I am also aware of the Lee U.S. Pat. No. 4,055,297 which describes the manner in which a solid fuel consuming furnace can be tied into a forced air heating system along with a conventional electric or fluid fueled heater. In the Lee system, the temperature at various points in the system is monitored and the control circuitry operates through motor arrangements to control the flow of heated air through the various ducts included in the system.
The present invention is more closely related to the system described in the Lee Patent than to those described in the aforereferenced Gifford and Biddle Patents, but differs significantly therefrom in the manner in which overall control is maintained. As such, it is believed that the present invention constitutes a significant improvement in the art.